My 03'Pontiac Montana quit shifting. The arm moves freely but nothing happens. I was told by a friend that a coupler connected to my shift arm was broken. how do I fix this coupler?

Appears to be a Prindle switch problem.(park, neutral safety switch)

U definitely have a mechanical issue. Hardest thing is getting down there to check it out.

U might ask a friend to get in the car and move the shifter so you can check movement under neath and see what it is not connecting with.

Linkage is disconnected.

Sounds like the linkage may have came off either the trans or the shifter.

have someone try to shift out of park then look if cable is moving at transmission ..if not moving then the cable could be unhook at steering column or defect.

hope it helps

Your manual linkage has come undone. You will need to determine what part of the manual linkage has broken, fallen off, or rusted through.

On that van, like many other GM front-wheel-drive vehicles, the shift cable goes through a bracket on the transmission to the linkage( the little metal arm). Where the cable connects to the linkage, there is a ball stud. It takes quite a bit of force to disconnect the cable from that. If it became disconnected at that ball without any other outside influence, the shift cable may need to be replaced. You can try pushing the plastic end of the shift cable back on to that ball stud ,it should click into place.
If the ball stud became disconnected from the linkage(little metal arm), the linkage would need to be replaced.
There should be a locknut holding the linkage to the transmission stud right above the range selector switch. If it came loose of there, you may need a new linkage, and to replace that nut

Drive until the sound appears and move the steering wheel left and right a little.Can you change the sound at all?If so it's wheel bearing time.

there is no linkage there is a cable fron the transmission to steering column nylon gromets on each end break replace shifter cable

replace the shift cable remove it and see if it moves freely if not replace if it moves freely check the shift mecanisim on the tranny if it moves freely then the problem is the shifter... take it apart clean it and reassemble.. this should do it...